1. Field of the Invention
The present invention relates in general to a liquid crystal display and a process for producing the same, and more particularly to a position-sensitive liquid crystal display applicable to various fields, especially to a thin input-output pad utilized for a pen-based computer or an electronic pocket notebook, which employs the liquid crystal display endowed with a position-sensitive function and a simple process for producing the same, exclusive of superimposing the liquid crystal display on a position-sensitive device.
2. Description of the Background Art
A conventional liquid crystal display, as the sectional view thereof is shown in FIG. 1, consists of a lower substrate, an upper substrate joined with the lower substrate and a liquid crystal.
The lower substrate comprises a polarizing screen 11 deposited on the lower surface 1 of a glass substrate, a pattern of a transparent picture element electrode 2 and a plurality of thin film transistors 3 formed on the glass substrate 1, a protective film 4 deposited over the pattern of transparent picture element electrode and the film transistors 3, and an error aligning layer 5 deposited, in sequence, on the protective film 4.
The upper substrate comprises the other polarizing screen 11 deposited on a glass substrate 1', a pattern of a black matrix formed on the lower surface of the glass substrate 1', a polyimide layer-coating color filter formed over the lower surfaces of the patterned black matrix, an adhesive layer formed on the lower surface of the color filter, a transparent counter electrode and an error aligning layer deposited, in sequence, on the lower surface of the adhesive layer.
The liquid crystal is injected between the lower substrate and the upper substrate.
Next, referring to FIG. 2, the description is given in detail for the conventional process of the production of the above liquid crystal display. Firstly, in step A, there is provided a glass substrate 1 on which a layer of transparent picture element electrode 2 is formed by the treatment of vapor-deposition and then is patterned. Thereafter, each of thin film transistors 3 is formed over the pattern of transparent picture element electrode 2.
Step B is undertaken to carry out to substantially finish preparing a lower substrate. For this, there is deposited a protective film 4 which plays a role in protecting a channel. Thereafter, an error aligning layer 5 is deposited on the protective film 4.
Subsequently in step C, a part of a process for preparing an upper substrate is started. The upper substrate is formed of a glass substrate 1'. A black matrix 6 is formed on the surface of the glass substrate 1' by the treatment of vapor deposition and then patterned in a desired shape. Thereafter, over the pattern of black matrix 6 is deposited a color filter 7 which allows red, green and blue colors to be expressed.
Step D is undertaken to carry out to substantially finish preparing the upper substrate. Initially, an adhesive layer 8 is applied to the color filter 7, Subsequently, a transparent counter electrode 9 and another error aligning layer 5' are deposited on the adhesive layer 8 in sequence.
Lastly in step E, a whole conventional liquid crystal display is produced. The lower substrate and the upper substrate are joined together in such a manner that the substrates 1 and 1' are directed toward the outside, respectively. A liquid crystal 10 is injected between the lower substrate and the upper substrate. Thereafter, a polarizing screen 11 is deposited on the outside-directed surfaces of the lower glass substrate 1 and the other polarizing screen 11 is deposit, ed on the outside-directed surface of the upper glass substrate 1'.
In the liquid crystal display that is produced by such a conventional process, the structure of the black matrix 6 that is formed in the upper substrate is given as shown in FIG. 3.
An image is displayed on the conventional liquid crystal display by a scanning signal and a video signal. In detail, each of the thin film transistors 3, which constitutes a picture element together with the patterned transparent picture element electrode 2, is selected by the scanning signal with generating the video signal. This video signal charges the patterned transparent picture element electrode 2, so that an electric potential difference is generated between the patterned transparent picture element electrode 2 of the lower substrate and the transparent counter electrode 9 of the upper substrate. As a result, depending on the difference, polarization of the liquid crystal is generated, which then permits a back light to pass through the liquid crystal 10. The polarized light further passes through the color filter 7 corresponding to each of the transparent picture element electrodes 2 and displays a color with a specific luminance.
However, the above-illustrated, conventional liquid crystal display performs only the function of display. Particularly, in case of a pen-based computer, an input and output is directly performed on a display element while using a pen. Accordingly, a conventional pen-based computer employs a pert input-output pad which is formed by superimposing the liquid crystal display, an output element, on a position-sensitive device, and an input element. However, this superimposition not only makes the input-output pad thick but also requires a technique for joining the two elements and adjusting for the joining. In addition, there is another problem in that a lower yield may result due to an error in joining the two elements together.